fix(sync): ignore stale invalid value responses

[aproskill81]

Closes: #1555

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Summary

Invalid/undecodable ValueSync responses are represented as Input::ValueResponse(request_id, peer_id, None).

Before this change, on_invalid_value_response penalized the peer before checking whether the request ID was still pending in sync state. This meant a stale invalid response could reduce a peer score even after the corresponding request had already been pruned or cleared.

This makes invalid responses consistent with the valid-response path, which already ignores unknown request IDs.

Changes

• Return early from on_invalid_value_response when request_id is no longer pending.
• Keep scoring and retry behavior unchanged for pending invalid responses.
• Add a regression test for stale invalid responses.

Tests

• cargo fmt --all --check
• cargo nextest run -p arc-malachitebft-sync invalid_value_response_ignores_unknown_request_id
• cargo nextest run -p arc-malachitebft-sync

[github-actions]

Hi @aproskill81,

Thank you for your interest in contributing to Malachite.

This PR has been automatically closed because you are not assigned to issue #1555. We require contributors to be explicitly assigned to an issue before submitting a PR.

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1. Comment on issue sync: stale invalid value responses can penalize peers #1555 requesting assignment
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